1. Field of the Invention
The invention relates to a calibrating method for adjusting signal driving parameters between chips and a related apparatus thereof, and more particularly, to a calibrating method for performing signal tests between chips to test a better driving force and a related apparatus thereof.
2. Description of the Prior Art
Electronic systems such as microprocessor systems have become highly important hardware foundations in our modern information society. A complicated electronic system utilizes many chips having different functions that co-operate with each other to achieve the complete function of the system. For example, a personal computer system comprises a CPU, chipsets (e.g. the south bridge/north bridge chipset or a chipset integrating the south bridge and north bridge), and a memory module. The chips are utilized to control data exchange between a peripheral device and the chipset. For example, a hard disk drive or an optical disc drive comprises a control chip to manage the data exchange. In addition, a graphic card, network card, and sound card can be regarded as sub-microprocessor systems, wherein each sub-microprocessor system utilizes one or more specific chips to achieve its function. Therefore, how to make all chips of the electronic system co-ordinate with each other in order to achieve the complete function of the electronic device is a key consideration of the design.
As known by those skilled in the art, each chip of the electronic device is installed in a circuit board (such as a printable circuit board, or the motherboard), and the chips are electronically connected to each other through the wires/traces of the circuit board. Considering the circuit characteristic, when a certain chip A has to transfer a signal to chip B, the signal outputting end of the chip A can be regarded as a power source (such as a current source) and the signal receiving end of the chip B can be regarded as a loading (such as a capacitor loading). Therefore, an electronic driving force (e.g. voltage or current) provided by the signal outputting end of chip A is injected through the wires of the circuit board into the signal receiving end of chip B such that the electronic levels (for example, the voltage level or the current level) can be driven appropriately. Chip B can read a value (content) of the signal according to the electronic level of the signal receiving end. The signal transferring operation is therefore completed. For example, in a normal digital electronic system, if the electronic level of the signal receiving end of chip B is higher than a certain predetermined reference value Vrp, chip B can determine it to be a digital signal “1”. On the other hand, if the electronic level is lower than a certain reference value Vrn, the chip B can determine it to be a digital signal “0”. Therefore, when chip A has to transfer a digital signal “1” to chip B, the driving force provided by chip A (here, the driving force can be called a positive driving force) should be enough to pull up the electronic level of chip B to the reference value Vrp such that chip B is able to determine the signal content of chip A correctly. If chip A has to output a digital signal “0” to chip B, the signal driving force provided by chip A (it can be called a negative driving force) should pull down the electronic level of chip B to the reference value Vrn such that chip B is able to correctly determine the signal content of chip A.
In the prior art, generally speaking, when a chip designer designs a chip, related parameters for signal receiving/transferring operations are embedded inside the chip. In other words, the driving force, which is utilized for transmitting signals, and the reference values for reading the signal contents are installed in the chip. Therefore, if the chips are operated correctly, the chips can receive/transfer signals according to the driving forces and the reference values such that data can be exchanged between the chips. For example, when a computer system is turned on, each chip of the computer system exchanges data according to the driving force/reference value in order to perform an initialization. Then the basic input/output system (BIOS) can be loaded, and the power-on self-test (POST) can be performed such that the booting procedure is completely performed.
When actually implementing an electronic system, however, many non-ideal factors influence the data exchange between chips. This makes the electronic driving force incorrectly drive the electronic level of another chip. For example, manufacturing inaccuracies in the chips may give rise to an insufficient signal driving force of the chip, or cause large impedance at the signal receiving end of a chip such that the electronic level is not easy to pull up or down. Furthermore, the impedance of the wire/trace may be too large (for example, the wire/trace may be too long, or the wire/trace distributed in different conducting layers), or the chip may be operated at a higher or lower temperature than desired. These factors may cause the driving forces/reference values migrations, resulting in the driving forces and the reference values not complying with the original design standards. Even if the chip utilizes the predetermined driving force to output signals, the predetermined electronic level may not be established in the receiving end of another chip. This results in the chip having problems reading the data transferred from the chip that transfers the signals. When this situation occurs in the computer system, the computer system may not correctly perform a booting procedure because each chip cannot smoothly exchange data and therefore the Basic Input Output System (BIOS) cannot correctly be loaded. In other words, the operational environment between the chips (e.g. the wires/traces of the circuit board, and the temperature) dynamically changes, and such variations may be too large to comply with the original designs. In the prior art, a fixed driving force and reference value is set in order to support the data exchange between the chips. Therefore, the prior art cannot sufficiently support the working environment when the chips operate.